The pending debt-ceiling relief bill would end a financial maneuver under way involving the Thrift Savings Plan’s most popular investment fund, although the process might be repeated in a matter of months unless a longer-term fix is put in place, the TSP said Monday.

The Treasury has “disinvested” the TSP’s government securities fund, or G Fund, in effect taking that obligation off the books to avoid a default on the national debt. That maneuver has been used many times in similar situations; both the TSP and Treasury have said that as in the past, accounts continue to be credited with interest and there is no impact on loans or withdrawals.

“It is worrisome to the participants,” Executive Director Greg T. Long said at the TSP governing board’s monthly meeting. “The fund is made whole, but we would rather it not happen.”

The House last week passed a bill that would not raise the limit but rather would set it aside until May 18. The Senate could take up that measure soon. After a debt-ceiling crisis has passed, G Fund securities are reconstructed.

That would happen with enactment of the pending bill even though that measure would not actually raise the limit, said TSP spokeswoman Kim Weaver. However, without such an increase, “we would start up again in May” with the disinvestment process, she said.

The G Fund held about 43 percent of the $330 billion on investment as of year-end 2012 in the 401(k)-style program for federal employees and military personnel. That was nearly twice the share of the next-largest fund, one tracking large-company U.S. stocks. The G Fund is the safest of the investment options, by definition never losing value and returning interest about at the level of midterm government bonds.

During December, investors engaged in something of a flight to safety, shifting a net $3 billion into that fund from the other funds. That was because “people worried about the ‘fiscal cliff,’ ” chief investment officer Tracey A. Ray told the board.

To date in January, she said, a net $3 billion has been moved out of the G fund and into the other funds. By making such shifts, those investors missed out on strong gains during December in the three stock-oriented funds — gains that have continued through this month.

Several board members expressed concern about such investor behavior and asked whether the TSP could generate individual data showing the difference between trying to time markets and staying with an investment strategy.

Board member Ronald D. McCray said that while the TSP does not give investment advice, it could tell investors that “you might want to think about what if you had stayed put — causing people to think about the consequences of their investment choices, for better or worse.”

Long agreed that TSP market timers experience “likely a lesser performance than if they had stayed put” and said the TSP is looking into how it could generate such data. However, that could be a multi-year project, he said.

The TSP’s year-end data presented at the meeting also showed nearly $130 million in Roth-type balances in the half-year since that type of investing has been allowed in the program. Weaver said the agency is waiting on IRS guidance on allowing investors to convert traditional balances to Roth balances, although paying a potentially hefty tax bill. The TSP and similar retirement savings programs received that authority as part of the fiscal cliff tax law enacted this month.

After receiving the guidance, the TSP will decide whether to make that option available. “To my knowledge, we haven’t gotten a huge outcry” from investors wishing to make such a change, she said.

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